Colors represented here are approximations and at best require a millions of color computer monitor adjusted correctly to view them.
The colors as represented do not show the metallic luminosity of the bright steel surface on which the colors are transparently overlaid.
For true colors a sample should be made of polished steel.
Printed the colors above may or may not print as they are HTML "background".

1 Machinery's Handbook, 18th Edition, 1970, Industrial Press
(Color text the same from 5th to 20th Editions with exception of the addition of Light blue at 640°F)

4 ASM Heat Treaters Guide,
Hardness data compiled from graphs by author September 2006 using this and other references in agreement.

Note that maximum hardness and tempered hardeness vary as much as 2 points Rockwell depending on the chemistry of the steel within its specification range.
An increase in carbon or manganeses makes deeper hardening steel and less makes it slightly softer and not as deep hardening.